In 3rd Generation Partnership Project (3GPP) that is a standardization project, a standardization process for Evolved Universal Terrestrial Radio Access (which is hereinafter referred to as EUTRA) that realizes high-speed communication has been performed by employing flexible scheduling in prescribed frequency and time units, which is referred to as an Orthogonal Frequency-Division Multiplexing (OFDM) communication scheme or a resource block.
Furthermore, in 3GPP, discussions on Advanced EUTRA that realizes higher-speed data transfer and has upper compatibility with EUTRA have taken place. In EUTRA, a communication system is available on the assumption of a network in which base station apparatuses have almost the same cell constitution (cell size). However, in Advanced EUTRA, a study on the communication system has been conducted on the assumption of a network (heterogeneous wireless network or Heterogeneous Network) in which base station apparatuses (the cells) having different constitutions are present in a mixed manner in the same area.
A study has been conducted on a dual connectivity technology in which, like in the heterogeneous network, in the communication system in which a cell (macro cell) having a large radius and a cell (small cell) having a smaller radius than the macro cell are arranged, a terminal device makes a connection to the macro cell and the small cell at the same time and thus performs communication (NPL 1).
In NPL 1, a study has been conducted on a network in which it is assumed that, when the terminal device makes an attempt to realize the dual connectivity between the cell (the macro cell) having a large radius (cell size) and the cell (the small cell (or a pico cell)) having a small radius, low speed is caused and delay occurs in a backbone (backhaul) line between the macro cell and the small cell. That is, there is a likelihood that delay in giving and taking control information or user information between the macro cell and the small cell will make it difficult or hard to realize a function that can be realized in the related art.
Furthermore, in NPL 2, a method is disclosed in which, when the terminal device makes connections at the same time to multiple cells that are connected to one another with high-speed backhaul, channel state information in a cell is fed back.